The potential offered by biomass and solid wastes for solving some of the world’s energy problems is widely recognised. The energy in biomass may be realised either by direct use as in combustion, or by upgrading into a more valuable and usable fuel such as fuel gas, fuel oil, transport fuel or higher value products for the chemical industry. This paper is concerned with conversion and upgrading by thermochemical conversion. It briefly describes the technologies of gasification, pyrolysis and liquefaction of biomass with particular reference to the use of catalysts. In addition, the use of catalytic processes in upgrading primary products from thermochemical conversion to higher quality and value fuels and chemicals is included.